This invention relates to a workhead for grinding machines having a spindle that is rotatable and is displaceable axially in an automatic manner in order to carry a workpiece toward and away from a grinding wheel.
Commonly, the workpiece to be ground is supported and caused to rotate, during the machining operation, by a workhead, while the grinding wheel, also revolving, is advanced towards the workpiece.
The workhead comprises a frame which is slidable on the machine table and can be fixed in any desired position thereon, and a spindle which is rotatably mounted on bearings on the frame, and caused to rotate by an electric motor connected by means of a belt drive. The spindle is provided with locking means for the workpiece, normally pincers, by means of which the workpiece is centered on the spindle and fastened thereto.
The aforementioned workpiece spindle is also movable axially on the frame in order to permit the axial displacement of the workpiece towards the grinding wheel; during which displacement particular machining operations can be accomplished, such as the grinding of a shoulder interposed between two cylindrical portions of the workpiece. The axial movement of the spindle is normally accomplished by means of hand-operated devices having graduated indicators provided with suitable points, by means of which the micrometric displacements are measured.
The workheads of the kind described above also have a number of drawbacks. First of all, the displacements of the spindle correspond only approximately to the theoretical displacements desired, owing to the lack of accuracy of the indicators and therefore, during machining, direct controls or measuring devices such as micrometrics on the workpiece are normally required. Further, workheads where the axial movement of the spindle is actuated manually, requiring a direct intervention by the operator, do not lead themselves to use with automatic machines having numerical control units, by means of which predetermined working cycles are accomplished in an automatic manner.